ES3036783T3 - Data communication cable having modified delay skew - Google Patents

Abstract

Twisted-pair data communication cables with modified delay values for improved electrical performance are described. Manufacturing methods and cable usage are also described. (Automatic translation using Google Translate, not legally binding)

Description

DESCRIPTION

Modified delay deviation data communication cable

REFERENCE TO RELATED APPLICATIONS

[0001]The present application claims priority of U.S. provisional patent application serial no. 62/621,234, entitled DATA COMMUNICATION CABLE HAVING MODIFIED DELAY SKEW, filed on January 24, 2018.

TECHNICAL FIELD

[0002]The present description refers, in general, to data communication cables that have desirable and improved electrical characteristics.

BACKGROUND

[0003] Twisted-pair data communication cables, such as Category 5e, Category 6, Category 6A, and Category 7 cables standardized by ISO/IEC 11801, provide high-performance data communication over relatively long distances using multiple twisted pairs of wires. In these types of data communication cables, the twisted pairs use differential signaling to attenuate electromagnetic interference and reduce crosstalk between adjacent twisted pairs. However, further improvements to such data communication cables, for example, to increase data transmission speed or the effective operating length of the cable, have traditionally required foaming the cable components or adding cable shielding. Both modifications have several undesirable characteristics, including higher cost, greater manufacturing difficulty, and reduced cable flexibility and durability. Patent document EP2530685A1 describes data communication cables comprising an insulating layer comprising FEP and titanium dioxide.

SUMMARY

[0004]According to one embodiment, a communication cable includes a cable core and a cladding layer surrounding the cable core. The cable core includes a first twisted pair of wires having a first twist length and a second twisted pair of wires having a second twist length, the second twist length being shorter than the first twist length. The first twisted pair of wires includes two insulated wires, each of which includes an insulating layer formed by a fluoropolymer and a propagation velocity modifier. The propagation velocity modifier comprises titanium dioxide. The insulating layer of each of the two insulated wires of the first twisted pair comprises between 0.2% and 0.45% by weight of the propagation velocity modifier. The communication cable exhibits a delay deviation of approximately 45 nanoseconds or less over a cable length of 100 meters.056

[0005]According to another embodiment, a communication cable includes a cable core and a sheathing layer surrounding the cable core. The cable core includes a first twisted pair of wires having a first twist length and a second twisted pair of wires having a second twist length. The first twisted pair of wires includes two insulated wires, each of which includes an insulating layer formed by a fluoropolymer and a propagation velocity modifier. The propagation velocity modifier comprises titanium dioxide. The insulating layer of each of the two insulated wires of the first twisted pair comprises between 0.2% and 0.45% by weight of the propagation velocity modifier. The second twisted pair of wires includes two insulated wires, each of which includes a foamed insulation layer. The first twist length is the longer twist length of the communication cable, and the second twist length is the shorter twist length of the communication cable. The communication cable exhibits a delay deviation of approximately 45 nanoseconds or less over a cable length of 100 meters.

DETAILED DESCRIPTION

[0006] Twisted-pair data communication cables are standardized according to various standards, such as ISO/IEC 11801 and TIA-568-B, which define, among other qualifications, the required electrical performance of the cables. For example, the ISO 11801 standard of the International Organization for Standardization (ISO) and the TIA-568-B standard of the Telecommunications Industry Association (TIA) require that twisted-pair data communication cables have a delay deviation of less than 45 nanoseconds over a cable length of 100 meters. As used herein, "delay deviation" indicates the time difference between the propagation delay of the fastest twisted pair and the slowest twisted pair, where propagation delay is the time required for a signal to propagate from one end of the twisted pair and be received by the other end of the twisted pair.

[0007]The propagation delay of a twisted pair is influenced by several factors, including the conductive material of each wire, the insulating material surrounding each wire, and the twist rate (measured by the twist length) of each twisted pair. Specifically, these factors determine the effective propagation speed of a signal transmitted through the twisted pair. As you can see, a twisted pair with a shorter twist length, or a tighter twist (the twist length indicates the degree of twisting and can be determined by measuring the distance between two consecutive sections of the twisted pair that have identical geometry), will have a greater propagation delay than a twisted pair with a longer twist length, or a looser twist, because the signal has to travel a longer effective distance due to the tighter twist.

[0008]This description generally refers to twisted-pair data communication cables with enhanced electrical characteristics, where the delay deviation is effectively modified. In particular, this description outlines procedures for modifying the propagation velocity of specific twisted wire pairs to achieve a desirable delay deviation for the overall twisted-pair data communication cable (e.g., approximately 45 nanoseconds or less over a cable length of 100 meters). Twisted-pair data communication cables exhibiting desirable asymmetric delays are described below, while incorporating twisted wire pairs with greater differences in the twist lengths between the pairs. These cables can leverage the modified delay deviation to improve the difference in run lengths.

[0009]As can be seen, modifying the propagation speed of certain twisted-pair wires can allow a twisted-pair data communication cable to include twisted-pair wires that exhibit a relatively greater difference in run lengths than a comparative cable that does not have twisted-pair wires with modified propagation speeds. For example, a twisted-pair wire modified to have a slower propagation speed can have a longer twist length (and therefore a shorter run) while maintaining the same propagation delay as a comparative twisted-pair wire whose propagation speed has not been reduced. Conversely, twisted-pair wires with a higher propagation speed can have a shorter twist length, maintaining the same propagation delay as a comparative twisted-pair wire that has not increased its propagation speed.

[0010] The greater differences in wire lengths, while maintaining the same delay deviation, allow the twisted-pair data communication cables described herein to exhibit improved electrical performance. For example, by increasing the difference in run lengths between each of the twisted wire pairs in a twisted-pair data communication cable, the cable can minimize crosstalk between adjacent twisted wire pairs and can meet higher rating standards without requiring, for example, additional shielding around each of the twisted wire pairs. However, as can be seen, the present invention contemplates twisted-pair data communication cables that include such shielding to achieve additional performance in certain embodiments. Generally, the propagation velocity of the twisted wire pairs can be affected by modifying the insulating material surrounding the conductive material of each wire in a twisted wire pair. The propagation speed can be calculated using the equation: VOP = 100/(DC)05, where VOP is the propagation speed (i.e., the propagation velocity) and DC is the dielectric constant. To reduce the propagation speed of a twisted-pair cable, a material with a higher dielectric constant than that of the insulation can be added to the insulation of each wire in the pair. Conversely, to increase the propagation speed of a twisted-pair cable, a material with a lower dielectric constant than that of the insulation can be added to the insulation. Collectively, these materials are referred to as "propagation speed modifiers" in this document.

[0011]Alternatively, the insulating material can be foamed to incorporate air (which has a dielectric constant of approximately 1.00059) and increase the propagation speed. In certain embodiments, twisted-pair data communication cables can incorporate propagation speed modifiers solely to decrease the propagation speed. In certain embodiments, propagation speed modifiers can be used to reduce the propagation speed of certain twisted-pairs and to increase the propagation speed of other certain twisted-pairs. In certain embodiments, twisted-pair data communication cables can decrease the propagation speed of one or more twisted-pairs using a propagation speed modifier and can foam the insulation of one or more twisted-pairs to increase the propagation speed of the other twisted-pairs.

[0012]In certain embodiments, a twisted-pair communication cable may be further modified with a wire separator to adjust the propagation speed. In such embodiments, an asymmetric wire separator may be used.

Twisted pairs. For example, the twisted pair with the longest arrangement (i.e., the fastest propagation speed) can be positioned further distally from the center of the twisted-pair communication cable. This distal adjustment can result in a larger pitch circle diameter and increase the effective transmission length of the twisted pair. As a result, the faster twisted pair may have a slower effective propagation speed. As can be seen, an asymmetrical cable separator can be asymmetrical for any number of twisted pairs. For example, each twisted pair can be positioned distally at a different distance from the center of a twisted-pair communication cable, or only a single twisted pair can be positioned at a different distal distance. In certain embodiments, a twisted-pair communication cable can modify the delay deviation and propagation speed using only an asymmetrical cable separator.

[0013]As can be seen, the inclusion of a propagation velocity modifier can be particularly advantageous, since the propagation velocity modifier can be used with any type of insulation. For example, propagation velocity modifiers can be used with fluorinated insulating materials, such as fluorinated ethylene propylene, which exhibit superior fire resistance compared to, for example, polyolefin materials. In certain embodiments, the use of a propagation velocity modifier can enable a twisted-pair data communication cable to pass the Underwriters Laboratory (UL) Plenum Steiner Tunnel 910 (1998) combustion test and demonstrate performance similar to that of a twisted-pair data communication cable made of polyolefin.

[0014]As can be seen, known twisted-pair data communication cables typically modify delay deviation by foaming the insulation of the wires in the shortest configuration (i.e., the one with the slowest propagation velocity) to increase the propagation velocity. However, fire-resistant insulating materials, such as fluorinated ethylene propylene, have poor foaming capabilities and are easily crushed. The twisted-pair data communication cables described herein overcome these problems by eliminating the need to apply foam of fluorinated insulating material through the inclusion of a propagation velocity modifier.

[0015]Suitable propagation velocity modifiers are not usually limited and can include any material that is compatible with the insulating material and has a suitable dielectric constant. In certain embodiments, titanium dioxide can be advantageously selected as a propagation velocity modifier to slow the propagation velocity. As can be seen, titanium dioxide is compatible with most insulating materials, has a high dielectric constant (between 86 and 173, depending on the form), and is also a common component already used in the manufacture of insulation for twisted-pair cables. When used as a propagation velocity modifier, titanium dioxide can be used at relatively higher concentrations than when used as a white colorant. In certain embodiments that include titanium dioxide as a propagation velocity modifier, an insulating layer may include titanium dioxide by incorporating from approximately 2% to approximately 20% by weight of a titanium dioxide master mix containing from 10% to 30% titanium dioxide, or any whole range between approximately 2% and approximately 20% by weight, such as approximately 3% to approximately 15%, approximately 4% to approximately 8%, etc. In certain embodiments, the insulating layer may include titanium dioxide in a proportion of from approximately 0.2% to approximately 1.5% by weight, or in any range between approximately 0.2% and approximately 1.5%, including approximately 0.3% to approximately 0.45%, etc.

[0016]In certain embodiments, other examples of suitable propagation velocity modifiers that can slow the propagation velocity may include titanates such as strontium titanate, barium strontium titanate, barium titanate, and calcium copper titanate, as well as zinc sulfide. As can be seen, such a propagation velocity modifier may have a higher dielectric constant than the dielectric constant of the materials used to form the insulation, such as fluorinated ethylene propylene.

[0017]Propagation velocity modifiers that slow the propagation velocity can have an additional effect that further reduces the propagation velocity. As can be seen, the impedance of a cable is determined by the equation: IMP = 276 / d Ca05 x Log(D/r) where IMP is the impedance, DC is the dielectric constant, D is the diameter of the insulated cable, and r is the radius of the conductor. Therefore, the inclusion of a propagation velocity modifier with a higher dielectric constant, such as a propagation velocity modifier that slows the propagation velocity, can decrease the impedance of the twisted pair of wires that includes said propagation velocity modifier. As can be seen, twisted-pair data communication cables are designed to have an impedance of 100 ± 5 Ω. To return the cable to the designed impedance of 100 Ω, the insulation thickness of the modified twisted pair of wires can be increased. Increasing the thickness of the modified twisted wire pair can increase the length of the helical path of the twisted wire pair, which can further increase the propagation delay.

[0018]When the insulating material surrounding the conductive material of each wire in one or more of the twisted-pair wires is partially or fully foamed, the foaming can be achieved by known techniques, such as incorporating a foaming agent or using reactive components. Typically, the insulating material can be foamed to any suitable foaming ratio, including ratios of approximately 1% to 90%, as well as any ratio between approximately 1% and 90%, including approximately 1% and 50%, approximately 5% and 30%, and approximately 6% and 15%. As can be seen, the foaming ratios can vary depending on the different insulating materials. For example, suitable foaming ratios for FEP may be approximately 30% or less. However, in certain embodiments, the twisted-pair data communication cables described herein may be foam-free.

[0019]As can be seen, the present description can improve the performance of a twisted-pair data communication cable while requiring the modification of only one pair of twisted wires. However, modifying two or more twisted wire pairs can further improve a cable's performance. As can be seen more clearly, modifying the propagation speed of one twisted wire pair can facilitate further improvements by allowing the delay deviation to be modified with a high degree of precision by varying the amount of propagation speed modifier included. Improvements in data deviation can allow the twisted wire pairs of a cable to exhibit a greater difference in twist length.

[0020]As can be seen, the remaining components of a twisted-pair data communication cable as described herein may be similar in design to the category 5, category 5e, category 6, category 6A and category 7 cables standardized by ISO/IEC 11801.

[0021]For example, each of the insulated wires of the twisted pair may include a conductor and an insulating layer. The conductor may be solid or stranded and may be made of any suitable conductive metal, including one or more of copper, aluminum, steel, and silver. In certain embodiments, the conductor may advantageously be made of copper due to copper's high electrical conductivity relative to its volume.

[0022]As can be seen, braided wire can be advantageous in certain embodiments due to the mechanical and electrical advantages it offers. For example, braided wires can exhibit greater flexibility and conductivity compared to a solid wire of the same gauge. In certain embodiments, the conductor wire can be a braided copper wire.

[0023]Generally, insulated wires can be of any suitable wire gauge. For example, in certain embodiments, the insulated wires may be sized according to the American Wire Gauge (AWG) standard, and each wire may be between 18 AWG and 32 AWG. For example, suitable insulated cables may be 26 AWG or 24 AWG insulated cables in certain embodiments. As can be seen, the selection of wire gauge can vary depending on factors such as the desired operating distance of the cable, the desired electrical performance, and physical parameters such as wire thickness.

[0024]Insulated wires can be coated with any suitable insulating material that can provide the desired electrical properties. For example, suitable insulating layers can be formed from dielectric materials such as polyolefins (e.g., polypropylene, polyethylene, etc.) or fluoropolymers (e.g., fluorinated ethylene propylene (FEP), ethylene chlorotrifluoroethylene (ECTFE), perfluoromethyl alkoxy (MFA and PFA), polyvinylidene fluoride (PVDF), etc.). In certain embodiments, selecting a fluoropolymer can be advantageous due to the superior electrical properties (e.g., dielectric properties and dissipation factors) and fire-resistance properties of these materials compared to polyolefins. In certain embodiments, the twisted-pair data communication cables described herein can use fluorinated materials for the insulated wires and can pass the UL 910 Plenum Steiner Tunnel combustion test. In certain embodiments, the insulating layer can be formed from an FEP polymer. As can be seen, in certain embodiments, different insulating materials can be used for different wire pairs. Twisted pairs. The use of different insulating materials can be advantageous for cost reasons or to further adjust the dielectric properties of the twisted wire pairs.

[0025]As can be seen, the selection of the insulating material may require balancing multiple properties. For example, FEP polymers that exhibit desirable electrical performance typically have a lower dielectric constant than FEP polymers with less desirable electrical properties. The inclusion of a propagation velocity modifier allows the use of a single insulating material for all twisted wire pairs, while also allowing for adjustment of the dielectric performance.

[0026] The insulation thickness can vary depending on the desired electrical performance. For example, each insulated wire in a twisted pair can have an insulation thickness of between 0.05 mm and 0.40 mm in certain embodiments, between 0.10 mm and 0.30 mm in certain embodiments, or between 0.17 mm and 0.25 mm in certain embodiments. As can be seen, the thickness of the insulation layer can also vary depending on the conductor size. For example, 24 AWG insulated wires may have an insulation layer approximately 0.25 mm thick, while 26 AWG insulated wires may have an insulation layer approximately 0.17 mm thick. The insulation resistance can be approximately 1,000 mΩ/km or higher.

[0027] As can be seen, the insulation may include additives, other than a propagation speed modifier, such as processing aids or dyes in certain embodiments. For example, it is common to include blue, green, brown, and orange dyes to facilitate the termination of twisted-pair data communication cables.

[0028] Insulated wires may be twisted together in pairs to form a twisted pair of wires, which may in turn be twisted together to form a cable core, as known in the art. In certain embodiments, a cable separator, such as a crosshead, may be included to provide additional separation between each of the twisted pairs of wires. In certain embodiments, the cable separator may be foamed to improve fire resistance and electrical performance. Cable shields may optionally be included around each twisted pair of wires and, in addition or alternatively, may be included around the cable core in various embodiments. A cable jacket may surround the remaining cable components. Examples

[0029] Inventive example 1 is a data communication cable having four twisted pairs. One of the four twisted pairs was prepared with a higher level of titanium dioxide loading. Specifically, the orange twisted pair contained 8% by weight of a titanium dioxide master blend with 10% to 30% titanium dioxide. The orange twisted pair had the longest twist length. The ratio of the longest to shortest run lengths of the twisted pairs in a fully sheathed cable was 1.65. Each twisted pair had insulation formed from fluorinated ethylene propylene (FEP) with a dielectric constant of 2.03–2.04 and a UL 94 flammability rating of V-0. Inventive example 1 further included a 155-thousandths-of-an-inch cross-sheet and a shield formed of 2-thousandths-of-an-inch-thick laminated aluminum with 0.5-thousandths-of-an-inch-thick polyethylene terephthalate laminated on both sides. The conductors were solid copper, 23 gauge according to the American Wire Gauge (AWG) standard.

[0030] The inclusion of high levels of titanium dioxide in the orange twisted wire pair resulted in an improvement in the deviation rate of 2 to 8 nanoseconds compared to a similar data cable formed with 1% titanium dioxide master mix. The improvement in deviation is believed to be due to a slower propagation speed of the orange twisted wire pair in inventive example 1. The observed improvement in the delay deviation rate means that the propagation delay (e.g., the time required to propagate a signal 100 meters) of the orange twisted wire pair (having the longer twist length) in inventive example 1 was 2 to 8 nanoseconds slower than the propagation delay of the similar twisted wire pair in the comparative data cable. As can be seen, improvements in the deviation rate, by increasing the difference in twist length between the longest twisted wire pair and the other twisted wire pairs, as described herein, can be used to improve the electrical performance of a cable.

[0031] Inventive example 2 evaluated the electrical properties of a copper conductor coated, by weight, with 96% FEP and 4% titanium dioxide in the form of a master blend. The FEP had a dielectric constant of 2.03-2.04 and a UL 94 flammability rating of V-0. The titanium dioxide concentrate included between 10% and 30% titanium dioxide.

[0032] The insulating layer of inventive example 2 was determined to have an increased dielectric constant of 2.07 at a frequency of 1 MHz, compared to an unmodified dielectric constant of 2.03 to 2.04, when calculated from observed capacitance measurements. The insulating layer of inventive example 2 was determined to have a titanium dioxide concentration of between 0.3% and 0.45%.

Claims (13)

I. A communication cable comprising: a cable core comprising: a first pair of twisted wires having a first twist length and comprising two insulated wires; and a second pair of twisted wires having a second twist length, the second twist length being shorter than the first twist length; and where the two insulated wires of the first pair of twisted wires each comprise an insulating layer formed from a fluoropolymer and a propagation speed modifier comprising titanium dioxide, the insulating layer of each of the two insulated wires of the first pair of twisted wires comprising between 0.2% and 0.45% by weight of the propagation speed modifier; and a sheathing layer surrounding the wire core; where the communication cable exhibits a delay deviation of 45 nanoseconds or less over a cable length of 100 meters. 2. The communication cable according to claim 1, wherein the ratio between the first twist length and the second twist length is 1.64 or higher. 3. The communication cable according to claim 1 or claim 2, wherein the fluoropolymer comprises fluorinated ethylene propylene. 4. The communication cable according to claim 1, wherein the insulating layer of each of the two insulated wires of the first twisted pair comprises between 0.3% and 0.45% by weight of the propagation speed modifier. 5. The communication cable according to any of the preceding claims, wherein the insulating layer of each of the two insulated wires of the first twisted pair of wires has a dielectric constant of 2.07 or higher at 1 MHz. 6. The communication cable according to any of the preceding claims, wherein the first pair of twisted wires has a propagation delay of 2 nanoseconds to 8 nanoseconds slower than the propagation delay of a comparable twisted wire pair formed without the propagation speed modifier. 7. The communication cable according to any of the preceding claims, wherein the second pair of twisted wires comprises two insulated wires; and where the insulating layer of each of the two insulated wires of the first pair of twisted wires has a greater thickness than the insulating layer of each of the two insulated wires of the second pair of twisted wires. 8. The communication cable according to any of the preceding claims, wherein the core of the cable comprises a plurality of twisted wire pairs and wherein two or more of the twisted wire pairs comprise insulated wires comprising the propagation speed modifier. 9. The communication cable according to any of the preceding claims, wherein the core of the cable comprises a plurality of twisted wire pairs and wherein one or more of the plurality of twisted wire pairs comprise insulated wires comprising a foamed insulating layer, the foamed insulating layers being free of the propagation speed modifier. 10. The communication cable according to any of the preceding claims, wherein the core of the cable comprises a plurality of twisted pairs of wires, each of which comprises two insulated wires; and where the insulation layer of each of the insulated wires comprises fluorinated ethylene propylene. II. The communication cable according to any of the preceding claims, further comprising an asymmetric cable separator, the asymmetric cable separator displacing the first pair of twisted wires distally outwards from the center of the cable core. 12. The communication cable according to claim 1 meets the requirements of the Plenum Steiner Tunnel 910 (1998) combustion test of Underwriter's Laboratory (UL). 13. The communication cable according to claim 1 meets the requirements of a category 5, category 5e, category 6, category 6A or category 7 cable, as defined in standard 11801 (2017) of the International Standards Organization (ISO) and the International Electrotechnical Commission (IEC).